For the purpose of increasing the photographic speed of a silver halide photographic material, various kinds of compounds have so far been examined.
In particular, it is well known that a certain amino compound, such as an alkylamine, ammonia, a hydroxyamine, a pyridine, an ethylenediamine, an imidazole, etc., is added to a silver halide photosensitive material or a developing solution in order to increase a photographic speed through acceleration of development. Details of effects brought about by such compounds are described in Research Disclosure, 17643, Vol. 176 (December, 1978); T. H. James, The Theory of the Photographic Process, 4th Ed., p. 424, Macmillan Publishing Inc. (1977), and so on.
However, although those amino compounds can increase the photographic speed through acceleration of development and so on, the methods suffer from the defect that fog density is considerably increased with the increase in photographic speed.
In addition, those amino compounds have little effect in rendering the gradation of a silver halide emulsion of high contrast.